Radio relaying system



June 23, 1942- F. H..KRoGER RADIO REL'AYING SYSTEM Filed May 15, '1940 5Sheets-Sheet 1 ifm.

INVENTOR FRED h'. KROGER ATTORNEY June 23, '1942- F. H. KROGER-RADIOZRELAYING SYSTEM Filed May l5, 1940 5 Sheets-Sheet 2 m as@ S MH .w

' ATTORNEY June 23, 1942. KRGER RADIO lRELAYING SYSTEM 5 sheets-sheet 4Filed May 15, 1940 WOS QWM.

FRED //FOGER ATTORNEY June 23, 1942 F. H. KROGER RADIO RELAYING SYSTEM 5Sheets-SheerI 5 Filed May 15, 1940 RJ Eg l m INVENTOR FRED H. K ROGER MMATTORNEY Patented June 23, 1942 f RADIO RELAYING SYSTEM Fred H. Kroger,Patchogue, N. Y., assignor to Radio Corporation of America, acorporation of Delaware Application May 15, 1940, Serial No. 335,217

(Cl. Z50-15) 20 Claims.

IThe present invention .relates generally to a radio relaying systememploying a plurality of repeater or relaying stations, and relatesspecically to methods of and means for efficiently relaying signals atultra short wavelengths, and also to circuit arrangements for indicatingat a central or division office the operating conditions existing at anyone or more stations of the relaying system.

The invention nds particular application to a radio relaying systemwherein there is employed at each repeater station an emergency powersupply system with vmeans for automatically switching the stationapparatus from the Ypublic power supply to the emergency power supply inthe event of failure in the public power supply system.Correspondingly,'the restoration of normal voltage to the public servicepower supply causes the station apparatus to be switched back from theemergency power to the public service power. In such a relaying systemit has also been suggested that two sets of amplifier equipment beprovided with means for automatically switching both the receiving andtransmitting antennae from one set to the other in case of a drop in orfailure of output for the transmitting antenna. For a more detaileddescription of a relaying system employing automatic switching orchange-over apparatus of the type described above, reference is hereinmade to my United States Patent, No. 2,017,126, granted October 15,1935.

An object of the present invention is to provide a circuit arrangementfor ruse with a relaying system of the type described above forindicating to a central oilice or division center which power supplysystem and/or which amplier equipment is in use at a particular relaystation. The terms division center or central cnice herein designate amaintenance center to which is assigned the responsibility ofmaintaining in working order a certain number of repeater stations inthe relay system, these stations constituting a zone. Where numerousrepeater or relay stations are employed, there may be several suchzones.

A further object is to conveniently and effectively control signaltransmitting apparatus at a radio repeater station from a remote pointwith a predetermined signal to which only the controlled station isresponsive.

Another object is to provide a radio repeater station in a relayingsystem with means which is selectively responsive to a predeterminedsignal transmitted fromthe central oce or division center for sending tothe central office a signal characteristic ci a particular circuitcondition at said repeater station. For achieving this purpose, there isprovided at the repeater station a circuit which automatically transmitsa plurality o f code signals indicative of vparticular circuitconditions then vexisting at that station.

A further object is to provide av radio relaying system especiallyadapted for the transmission of frequency modulated signals.

The present invention provides a system whereby the status of theindividual relay stations can be communicated to the division center atthe will of that center, in a way that requires only one communicationchannel which can also be used yfor other communication purposes.

A feature of the invention is a special circuit `arrangement at eachrepeater station including on to the next repeater station, atransmitter and associated transmitting antenna, two sets of amplifierapparatus (one automatically efi fective in case the other fails), anemergency power supply automatically effective in case the publicservice power supply fails, a selector or iilter associated with thereceiver and responsive to a characteristic signal for driving a motor,a plurality of rotatable code discs driven by the motor, a pair ofVcontacts associated with each code disc, a relay connected in common toall contacts and responsive to the movements of said contacts forcausing signals characteristic of r the code discs to be sent out bysaid transmitter,

and relay means associated with the amplifier and power supply equipmentfor rendering effective only those contacts and code wheels whichcorrespond to the code designation of the `particular equipment beingused.

In the accompanying drawings, Figs, la and 1b taken together illustratediagrammatically a complete radio relaying system many of whose featureshave been designed by me and successfully tried out in practice and towhich the principles of the present invention may be applied; Fig'. 2illustrates schematically apparatus at one repeater station of therelaying system for achieving status indication in accordance with oneembodiment of the invention; and Figs. 3 and 3a taken together showapparatus embodying the principles of Fig. 2 as applied to a repeaterstation, and also apparatus for performing additional functions.

'Ihe radio relaying system shown in Figs. 1 and la is designed for useparticularly with television signals, although it will be vunderstoodthat it may also be used to transmit telegraph signals or any type ofradio signal. The system includes a transmitting station A, a pluralityof intermediate repeater stations B and C, and a receiving station Dsuitably spaced apart along the line of transmission. Repeater stationsB and C are designed to repeat the signals from station A to station D.The arrows indicate the directions of the signals between the respectivestations. Although only two repeater stations have been shown, it shouldbe understood that this number is illustrative of any number of repeaterstations which may be located at frequent intervals along the line oftransmission for amplifying and reradiating the signals.

The antenna system indicated at the transmitting station A is shown tobe of the omnidirectional broadcasting type, having constantcharacteristics over a frequency band sufficiently wide to accommodatethe full band spectrum of high definition television. This antennaconsists of two separate, independent radiator systems I and 2, theformer for sound and the latter for vision transmission, both radiatorsbeing supported on a common column located at an appreciable distanceabove ground, usually on the top of a tall building. The antenna systemof the transmitting station A is of the type installed on top of `theEmpire State building in New York city, New York, and is described quiteadequateing and reradiating the signals to the next repeater orreceiving station along the line of transmission Since the transmissionrange of the ultra short waves at which this system is designed tofunction depends upon the air line or visual distance, a factorproportional to the height above the earths surface, it is proposed tolocate all stations at points having as great height as possible, suchas mountains, tall buildings, radio masts, etc. The receiving antenna 3at repeater station B consists of a pair of dipole arrays placed onebehind the other and suitably phased relative to each other forproviding a .unidirectional effect. This antenna is designed to receivethe signals transmitted from station A. Reference is hereby made toCarter United States Patent No. 2,183,784, granted December 19, 1939,for a suitable description of antenna 3. The reradiating or transmittingantenna 4 of station B is of the metal parabolic type which has as itsfocus a plurality of folded dipole antennas arranged in the samestraight line. The folded dipole antenna has been found to be much moreeffective than the single `dipole and is of a general form described incopending application Serial No. 155,385, led July 24, 1937, by PhilipS. Carter. At repeater station C there are shown a receiving antenna 5and a reradiating or transmitting antenna 6, both of the parabolic typeemploying folded dipole antennas, as described in connection withantenna 4 of station B. Antennas 5 and 6 are, of course, effective indifferent directions, the receiving antenna 5 being positioned toreceive the signals from station B while the transmitting antenna 6 ispositioned to transmit the signals in the direction of the next adjacentstation D. Antennas 5 and 6, as well as all the equipment at station C,are enclosed within a thin wooden cylindrical container 'I mounted on asteel tower. Aside from the metal bolts and screws employed in theconstruction of the wooden cylinder, there is no extra electricallyconductive material employed, mainly because I have found that thepresence of metallic strips or bands for the wooden cylinder causes adistortion in the `directivity pattern of the antennas and undesirablefeed-back therebetween, and also causes a loss in signal strength. Thewooden enclosure functions not only to mount the equipment and theantennas, but also prevents disturbances caused by wind pressures,sleet, ice and dirt from interfering with the normal characteristics ofthe antenna system and the associated apparatus. The commodious interiorof the Wooden container also simplifies the maintenance of the equipmentand enables suitable heating apparatus or other desired equipment to beprovided within the enclosures.

The antenna 8 at receiving station D comprises a parabolic reflectorhaving at its focus a plurality of folded up dipoles, this antenna beingof course directed to receiving the signals from antenna 6 of theadjacent repeater station. The antennas of stations A to D, inclusive,have been described as being of a particular type, mainly by way ofexample, since it is apparent that other types of antennas can be usedto achieve the desired results.

In the operation of the system of Figs. la and lb, television signalsemanating from broadcasting station A are amplitude modulated andradiated at a frequency of 45.25 megacycles and received on antenna 3 atstation B from which the signals pass to a 72 ohm coaxial cable 9 to atelevision receiver I0 to provide a Video component the band width ofwhich is 4 to 6 megacycles. This video output is used to control atransmitter with multi stages of frequency tripling. In order to convertthe signal into centimeter waves, the video component, through theintermediary of frequency modulator II, modulates a variable oscillatorI2, the output of which is at the mean frequency of 52.6 megacycles witha variation of plus or minus .33 megacycle. This output is passed on toa frequency tripler stage I3 which provides an output of 158 megacycleswith a variationof plus and minus 1 megacycle or higher, this lastoutput of 158 megacycles being passed on to a final tripler stage I4from which there is obtained an output of 474 megacycles with a .bandfrequency deviation of plus and minus 3 to 6 megacycles, and higher, ifdesired, which last output is passed on by a '72 ohm coaxial cable 40 tothe transmitting antenna 4. It will thus be seen that the amplitudemodulated waves of 45.25 megacycles received from transmitting station Ahave been converted into frequency modulated waves of a much higherfrequency, of an order near 500 megacycles. The vacuum tubes employed inthe tripler process, as well as in the final stage in a straightamplifier 'B to fsend .out test signals comprising a singlepicture'havingxaband width of from zero to 5 megacycles. There ris Valsovprovided a switch I1 which,. depending .upon 'the position in .which itis thrown, enables the :attendant at Ythe repeater station `B to observeonra kinescope I8 and an 'oscilloscopell the-output radiated overantenna 4 or the input received for the television receiver 1d. For thisvpurpose there is provided a monitorconverter which converts thefrequency modulation .from the final'stage of the tripler `Mito suitablevideo signal waves-which can be observed. Thefkinescope I8 provides thepicture signal :while the oscilloscope I9 shows the wave form of thesignal.

Atrrepeater station C'the receiving antenna 5 receives the 474nzegacycle `frequency modulated signal radiated by antenna 4 Vof stationB and covnertsthe signal by meansofa converter 2! to a 100 m'egacyclesignal ifor more eflicient amplification. This `liOU vmegacycle signalis ampliiied by :a three stageamplier 22 and then con verted in 123to anoutput frequency modulated signal having a mean frequency of 4Mmegacycles, which is then transmitted `by antenna -5 toward the nextadjacent station, in this case receiver'station D. Oscillators 2d-and'25, associated respectively with converters 2l and 23, function at374 and 364 ymegaoycles respectively to change the incomingr frequencydown from 474. megacycles to 100 megacycles `and then to kincrease thefrequency ofthe 100 megacycle component to 464 megacycles. Here again anamplieris provided betweenthe converterzland the `transmitting.antennai,and a monitor converter 26 is utilizedto provide video signals io thelocal kinescopeland oscilloscope 28. It should beobserved'at this timethat intermediate station C Aconverts the frequency modulated -wavesreceived on one frequency .into frequency modulated Waves of anotherfrequency whichare then reradiated.

At :the final receivingstation D in the relay link, the frequencymodulated 'signal is received on antennafa at Ai6/i megacycles 'andconverted by apparatus '29 to a 100 megacvclesignal which is then.passed on to an amplifier and limiter 3!! to a second `converter-3|which reduces the sign nal to 29 megacycles before it is passed on todetector 32 which transforms lthe frequency modulated signals toamplitude -modulauted signals. The output of detector 32 comprises videosignals which are amplified by amplifier 33 so that they Vcan besuitably observed by the local kinescope .34 and thevlocal oscilloscope35. Oscillators 36 and 31, associated respectively with the con vertersv29 and 3l, generate 364 megacycles and 129 megacycles respectively toreduce the signalsto'the frequency values mentioned above. If desired,the output fromfamplifier having a four-megacycle'band width-and highercan loe passed by .means of :cablei to a vsuitable estudiolfor."-'rebroadcasting over .a .second lloroadcasting .transmitter(not'rshown'k In the :radiolrelay embodiment l'shown in Figs. la `and5111i, and .successfully tried :out-in; practice,

.the transmitting .antenna .A was located i on :top

of the' Empire vState .buildingin .New York,A New York; :the repeaterstation B was located .at Hauppauge, Long Is1an'd,'New York, vabout 45milesavvayirom the EmpireState Building; the repeater station C waslocated at ARocky iPoint, Long Island, New Yorkywhich is about :fteenymiles from Hauppauge; and :the receiving station D was located :atRiverhead, ,Long'Island,

'New York, a distance of fifteen milesfrom -station C. These-distancesbetween the stationsy are .notto be `considered .asbeing limitativeincharacter, since the stations'tmaybe separatedffrom one :another anydesired-distance, so longas any two adjacent stations .sare within .theoptical range of visible distance. `This is because the electromagneticWaves `at the lower .wavelengths below ten meters, let lus say, withwhich therelay system of Figs. :1a fand lb are :particularly concerned,have characteristicsl which are fquasioptical in nature; that is, theyhave aivery delinite limited range -oftransmissionrwhich is cornparablewith the optical range.

Fig. 2 illustrates diagrammaticallya repeater station .equipped withapparatus .in accordance with the invention forautomatically. sending toa division center or central oiiicezaplurality of signals vforindicating the operating conditions existing at the repeater. Inthisfigure the receiver and transmitter.arediagrammatically indicated inboxform and appropriately labeled as such, and their respectiveassociated-antennas 40 and 4| are also diagrammatically indicated,although it will be understood that the antennas .as well ras ytheVreceiving and transmitting Aapparatuscan be of any suitablekin'd suchas, for example, those shown in repeater stationsB and C of Figs. la and1b.

At each repeater station, as lshown in`Fig. i2,

there is provided Va selector mechanism 43 responsive toa characteristicsignal for operatinga relay whosecontacts control a motor'M. On vltheshaft of the motor`M there are provided four code ldiscsrr', b', lc' and`d which are provided with segments according to a prearranged code.`The segments `of each code disc or wheel occupies less than"1180. Thesegments on disc a' Vare on the opposite 180 side from code disc c',.and correspondingly the segments for code discs lb and d' are oppositeto each other although respectively on the same`180 as a `and c', .asshown. This arrangement permits two code'i'signals to be transmittedwhen the motor operates, the possible combinations of-which are a .andc', .a and-d', b and c', and b and d'. 'Associated with 'each code discor wheel are a pair of contacts `45 which normally are open but arearranged to close when contacted by a raisedsegment on therdisc. lOneContact of each disczor zwheel .is connected to thecorrespondinglypositioned contact of .each of the other pairs, and'these correspondingly located contacts in turn'connected to Aoneterminal of the winding or a "relay '46,"the other terminal of which isconnected to the positive side of a battery-or suitable ysource ofunidirectional energy41. tacts'45, `4'5`is connected to acontact of oneof the relays 48, "4Q-or50. jThus,:the opposed fcontacts Yof relays48-andr`4`9 are connected' to dif- The other'contact of eachpair ofconferent contacts of code discs a and b', while opposed contacts ofrelay 58 are connected to different contacts of code discs c and d', asshown. The armatures of relays 43, 49 and 58 are connected together andto the negative terminal of battery 4'|. A spring 5| associated with thearmature of relay 50 normally pulls the armature 50 to the upper orbreak contact in the absence of energizing current through relay 58. TheWinding of coil 50 is connected to the public service power supply orsome apparatus associated therewith, so that when the apparatus at therepeater station is being energized from the public service power supplythe relay 5U will be operated and the armature will be pulled down toengage the make contact. Relay 48 is connected with one set ofamplifiers, while relay 49 is connected to the other set of amplifiers,so that depending upon which set of amplifiers is operated the relay 48or 49 will be energized, thus pulling the armature either up or down, orif the relays are positioned horizontally, to the left or to the right.The armature of each of the relays 48 and 49 will remain in the positionin which it is pulled until such time as it is pulled in the oppositedirection by energy in one of the relay windings. It will be obvious, ofcourse, that relays 48 and 49 may comprise a single relay of thepolarized type having a pair of windings. It is assumed, of course, asmentioned above, that the relay station is provided both with anemergency or spare power supply so that when the public power supplyfails the emergency or spare power supply immediately takes over theburden of supplying excitation energy to the receiving and transmittingapparatus at the repeater station, and correspondingly, that when publicpower service is restored the translating apparatus at the repeaterstation will automatically be switched or changed back from theemergency to the public service power supply. It is also assumed thatone set of amplifiers automatically replaces the other in the event offailure of one of these sets. The failure of one set of ampliers maymanifest itself when the radio output of the relay station is reduced toa value which causes the system to cease to function. This value neednot be absolute radiation failure. When this occurs, there will be ashift from one amplifier set to the other. Operation of the relaystation may be started and stopped by radio signals sent over the relaysystem. Obviously, the code disc wheels a', b', c' and d' can bereplaced by commutator wheels, and the contacts 45 by brushes orsuitable contacts engaging the commutator wheels. Thus, each commutatorwill have a predetermined number of contact segments separatedbyinsulating centers for sending out desired code signals, it beingunderstood that when the motor is at rest the contacts or brushes willengage an insulating sector.

The operation of the system of Fig. 2 will now be described. Assumingthat periodically, let us say, every hour or so the attendant at thedivision center desires information as to which pieces of apparatus arefunctioning at the different relay stations. To obtain this informationthe attendant at the maintenance center sends out a signal which ischaracteristic of a particular relay station from which information isdesired, it being understood that each station has a characteristicsignal different from the signals of the other stations. This signal maybe a code signal or,

vvamargo-i4.

preferably, a tone of constant frequency .and amplitude. Thistransmitted tone sent vout,.by the maintenance center is received overantenna 40 and the associated receiver and passed on through line 52 tothe transmitter and associated antenna 4| which transmits the signal onto the next station of the chain. A branch circuit 53 at each repeaterstation passes this tone to the selector 43 and if this selector isresponsive to the tone sent out by the maintenance center it will causethe operation of relay 44 which, in turn, will close its contacts overan obvious circuit tc operate motor M and cause the rotation of fourcode wheels a', b', c' and d'. The motor is so arranged that it willrotate the code wheels only once and the code wheels will again come torest in the position indicated in the drawings with the contacts opencircuited, unless the tone signal from the division center is beingcontinuously transmitted, in which case the motor will rotate for anintegral number of revolutions during which the characteristic signal isbeing received and passed by the selector 43. As the motor and thewheels rotate, the contacts 45 close in accordance with the codecharacteristics on the discs to operate relay 46 which in turn closesits contacts 54 to affect the transmitter over leads 55 to cause thistransmitter to send code signals to a division center. If desired. thesecode signals can be sent out continuously until stopped by themaintenance or division center. The code signals transmitted by therepeater station of Fig. 2 over antenna 4| may or may not be radiated inthe direction from which signals are received over antenna 48, dependingupon whether or not the transmitted code signals from the repeaterstation are received directly by the division center or through theintermediary of another division center. If the public service powersupply is being used, the relay 58 will be operated and will pull itsarmature down against the restraining influence of the spring 5|, thusclosing an obvious circuit through the winding of operating relay 46 andthe segments of code wheel d' when the motor is operated. However, ifthe public service power has failed and the emergency power supply isbeing used, the armature of relay 50 will be in its normal position andwill be contacting the upper contact, thus closing an obvious circuitfor code disc c' to send outl a different code signal. In the same way,the two sets of amplifiers operate on the relays 48 and 49 to conditioneither code wheel a' or code wheel U to send out code signals via relay46, it being understood, of course, that the codes are different for thevarious code wheels. Thus, during the operation of the motor M the codewheels will send out two consecutive signals, one indicating whether thepublic service power supply or the emergency power supply is functioningand the other indicating which of the two sets of amplifiers is beingused. As soon as the attendant at the division center obtains thisdesired information, he will 'cease sending the characteristic tonesignal, thus stopping the motor and restoring the shaft and code Wheelsto their normal rest position. This cycle of operations will be repeatedfor all the repeater stations within the zone of the division center.

Figs. 3a and 3b considered together illustrate a preferred and practicalcircuit embodiment which can be installed at each of the repeaterstations of the relaying system for indicating to the division centernot only the status of the amplier and power supply equipment, but alsofor indicatingv the noiselevelj and carrier level, as well as anyotherdesired condition of operation; The system of Figs. 3a and` 3b alsoincludes a'- start and stop arrangement for conditioning the repeaterstation tooperate or to shut down. In these last figures there are showna public service power supply-outlet indicated diagrammaticallyY as 33;an. emergency or spare power supply system indicated by the rotaryconverter 30 and battery 3|; a pair ofamplirler systems each including apreamplifier 64 or 65 and a power'amplier 6,6 or 61; switch-over devices22 and 23 for associating the receiving and transmitting antennae withthe particular preamplifierand power amplifier required for operation;time delay apparatus ||4 for isolating necessary automatic change-overat a particular station without interfering with the individualfunctioning of the other repeater stations; selector apparatus 6|, 62and 63for`selecting and passing to the propernrelay the tone signalsreceived over the service channel; code discs 66 for sending codesignals indicative of the status of the various pieces of equipmentatthe repeater stations; and various relays and switches associated withthe foregoing pieces of equipment.

In the operation of the system of` Figs. Saand.

3b, assuming that it is desired to start up the repeater station atwhich this apparatus is located, the remote central oice or divisioncenter (not shown). will send out a tone A over. the

service circuit, which may be either a wire lineY or a radio channel. Ifa radio-channelY is used for the service circuit, then it ispreferredthata narrow band of frequencies be used thereover which isoutside the range of the message waves, and that separate amplifiers andrepeating equipment (antennas, etc.) be used therefor at the repeatingstations than for the message waves. This start tone A will start up allthe relay stations in the system simultaneously and will be sent out forat least thirtyseconds. The start tone will be received at eachrepeatervstation and passed on to the selectonequipment where onlyselector 6| willv pass tone A1 through to a tone amplifier and rectifier10the latter producing a rectified current for operating relay |02. Theoperation of relay |02` will close its contacts andcauseA the operationofV relays ||0, |00, |04, |06V and |01. The path forv operating theserelays will be traced over a circuit from the positive-terminalfofbattery 3| through theoperating coilof" relay ||0, lead H5, contact ofrelay |02, lead H6, to one'terminal of the coils |06, |01, |00 and inparallel, through theseA coils to'lead H1, then tothe negative terminalof battery 3|.

When relay H0 operates, the closing of the left the plate and-filamentsupply leads 13, 'I4 and 15 and 16 for the preampliers and poweramplifiers, respectively. It should be noted at this time that relayVoperates when the public service Voltage is above a minimum valuedetermined by under-voltage relay 24, and it has been assumed that thisrelay! wasvoperated before the Voperation of; relay |.|0.V .Manuallyoperated switches .22,.23,. I8;` I9 and20 and 2| determine which set;-ofi amplifier equipment andtheir respective power. supply outletis to beused inthe normal operation of the repeater system rand which isv to.function asiaspare. Assuming that switches 2,2, and23 arethrown upward,andithat relays, |00 and |0|, nowy operated; pull their respective.armatures to the 1eft,.it will be obvious that the .transmission lineY|23-from the directive receivingantenna; andthe transmission line |24from thezdirective. transmitting. antenna; will. be connected: throughthe lefthand terminals O f the reversing switchesand the lefthandbladesof switches 22.and. 23. to;one.set of. power amplifier;

equipment comprising preamplifier 64 and. its associated; power'.amplier 66;. Thisstate of facts .requiresth'at switches I8 and20 bethrown down and switches. |.9..and 2|. .thrown up, in. order to supply.`power to. theplatesand. filaments 13 and 15lof. the .preamplifier 64:and power amplifier 66, respectively., throughtheoperated contacts of.relays. .|661 and..|01. .Theradiation of carriercurrent.overtransmission line |24 will occur in;some. thirty. secondsafter theoperation. of. relay |.|0. By. exposure to. this radiation throughproper coupling of. transmissionlines. |25 and. |26, radio frequencycurrentswilli. be passed on. to. diode 18 and converterv and rectifier19.. `The output of diode 18 will` pass` currentA over leads |28. andthrough rthe rwinding of relay |'.|3 .for enabling current toAbe-.supplied to ,the .holding winding of relaysf |00; .-|.0|,. :|013and. 0.6, the last. holding. winding,vnamely 10.6, .being operated bythe .intermediate oraccessory. relay |05', in-the manner .now to beldescribed; .The outputof this. diode 18 passing current .over..leads|.2Blwill .operate relay H3; thusbreak-ingthe normally. made contactsleadingv from the -motor ofthe time delay. relay. |4to-its power Supply.At thisrtime itshouldbe observedA that--the time-.delay relay. I4.` hadvits operating circuit closed uponltiieA operation of relaylildithroug-hapathextending over leads |21 and thenormall make contacts o fv relay||3, as-a consequence ofV which the-time.- delay relay ||4 (comprisingsome suitable motor arrangement such-asa telechron motor.,r here givenby wayvr of example only) .will rotatethe commutator |2| clockwise`through the shaft'. shown, andV cause theY segmented cam -|.20tocommence its trayel. Thecommutator |2|vwill-continue to rotateuntil theoperating4A circuit fon the time delay circuit |'|v4 is opened atYthefcontacts of relay H3. .The operation of relay ||3, which will occurapproximately-thirty-seconds aftertheinitiation of.. the start signal',-will stop the rotation of the time delay motor maintaining contact V| |9in about the mid positionY on onevof theelectrically conductcircuituntil cam |20 reaches the beginning of segment-position #1', sayforthirty seconds.

In the event that all repeater stations in the systemA which start`upsimultaneously function in intended manner. withA no failures inequipment, then. alloffltherepeater cams |20 at the variousstations willstop at the midposition of #l segment. The electrical circuit forthe'rst relay station in the system will be constructed to open at theend of the #l segment position on the cam. The circuit for the second ornext relay station will be constructed to open at the end of the #3segment position on its particular cam. The circuit for the thirdrepeater station will be constructed to open at the end of the #5segment position on its particular cam, while the circuit for the fourthrepeater station will open at the end of #9 sgment position, etc.

In the event that the amplier selected by operation of relays and I0|fails after having started to function, there will then be insufficientradiation over output transmission line |24, and insunicient output fromdiode 18 to maintain relay ||3 operated. The restoration of relay |I3 tonormal, caused by the failure of carrier current radiation and theconsequent failure of energy in leads |28, recloses the operatingcircuit for the motor of the time delay relay I I4 through a pathextending over the normal make contacts of relayv I I3. Relay ||4 willnow cause the commutator |2| to continue its rotation until such time ascontact ||9 leaves the particular operating segment on cam |20associated with this station and breaks electrical contact with thecommutator, at which time the motor will come to an automatic stop andwill maintain this condition until the entire system is shut down, atwhich time it will return to normal and contact ||9 and cam |20 will berestored to the'position shown in the drawings. As a consequence of theopening of the electrical circuit between contact I9 andthe particularoperating segment on cam |20, current will be removed from leads |22 andthe holding windings of relays |00, |0I, |06 and |01 and these relayswill return to normal. The return to vnormal of relays |00 and I0| willcause the respective armatures thereof to be drawn to their right-handpositions by their restoring springs, and will connect the transmissionlines |23 and |24, respectively, to the right-hand blades of switches 22and 23, respectively, and to the amplier equipment comprisingpreamplifier 65 and power amplifier 61 with their respective plate andfilament supply circuits 14 and 10, The restoration of relays |06 and|01 to normal will close their normal break contacts to provide a pathfor the power supply through the central contacts of relay I|0 andthrough the normally made normal break contacts of relays |06 and |01and through switches I9 and 2|, respectively, in their prescribedposition, to the plate and filaments of the electron discharge devicesassociated with the spare amplifier.

In the event that the second relay station in the relay system does notbegin to supply radiation because the normally selected amplifier doesnotfunction properly, the cam |20 at this station will continue torotate until the end of #3 segment is reached when the electricalcircuit between contact IIS and commutator |2| will be opened, and thespare amplifier at this station will be thrown into service. The cam |20at the first relay station, however, will be stopped in the midpositionof #l segment. As soon as radiation occurs from the second relaystation, the signal coming through the second relay station will stopall subsequent stations at the #3 segment position on their respectivecams.

In the event that the third relay station in the system does not beginto supply radiation because the normally selected amplifier does not hasgone before that the iirst tworelay stations will have stopped` in themidposition. of the #l segment on the cam, while the third station aswell as the subsequent stations will advance to the end of the segmentposition. At the end of the #5 segment position, the spare amplier atthe third relay station will be thrown into service and the radiation ofsignal therefrom will stop the cams at the subsequent stations.

The table below shows the position of the cams at the several repeaterstations under various function properly, it'will be apparent from what75 At start only relay sta- Relay station #l Relay station #2 Relaystation #3 Relay Relay station #4 station #5 Start with tone A-nofailure tion #5 falls At start only relay station #4 fails At start onlyrelay station #3 fails At start only relay station #2 fails At startonly relay station #l fails I f all start O. K. and

then station #5 fails If all start O. K., and then stations #5 and #4fail in succession 1 1 1 9 If all start O. K., and then stations #5, #4and #3 fail in succession If all start O. K., and then stations #5, #4,#3 and #2 fail in succession 1 3 5 9 If no station starts O. K 2 3 5 9If all start O. K., then station #4 fails l 1 1 9 9 If al1 start O. 'K.,then station #4 and then station #3 fails l l 5 9 If all start O. K.,then station #4, then station #3, then station #2 fails 1 3 5 g If allstart O. K., and then stations #4, #3, #2 and #l fail in success1on 2 35 9 If all .start O. K., and stations #4, #3, #2, #l and #5 fail insuccession 2 3 5 9 From the foregoing, it will be seen that the startingtone A starts all the cams at the various repeaters together, but thesignal coming through stops the cams.

One advantage of the present invention lies in the fact that if thediode current in diode 18 fails in any one repeater station, causing atransfer to the spare amplier, the subsequent repeater stations in thedirection of transmission Y need not transfer to the spare amplifier.

In the event that the public service power supply fails eithercompletely or falls below a minimum prescribed voltage determined by theunder-voltage relay 24, the relay will return to its normal position andthe emergency or spare power supply comprising rotary converter 30 andbattery 3| will be connected to the system through a path including thepositive terminal of battery 3|, through lead |29, through armature andfield in parallel of rotary converter 30, lead |30, intermediate breakcontacts of relay III, lead |3I, right-hand operated contact of relayIIO, lead |32, meter 32 to the negative terminal of battery 3|. Theemergency or spare power supply equipment will pass power through leads|33 and closed switch 35, leads |34,A and normally made or breakycontacts ofy relay III to voltage. regulator. 28 and then over acircuitpreviously` described to relay I it for. supplyingA power to theY platesand filaments of theV amplifiers. Thechange-over from the public powersupply tothe emergency supply is designed to be so rapid upon failure ofthe public service power supply that the relays maintain their normaloperating vpositions without any interruption whatever,.due tothechangeover. As soon asthevoltage. on the public service supplybecomes normal, a change-over is again effected from the spare oremergency power supply to the public service supply by the operation ofrelay in a manner previously described. While the. system is on thepublic service power supply, the battery 3| is kept charged throughVRectox unit 29 and` its associated transformer 29a and the enclosedswitch 34. This chargingis regulated by the ampere-hour meter 32.

If the division center desires to know the status .of the apparatus atthe repeater station, a

' tone ,C will be sent out over the service circuit and passed throughselector 53 to be amplified and rectified at 'l2 in order to operaterelay |95, the. latter upon operation closing its contacts to operatemotor 25 over a path including leads |35 which extend to the,alternating current powersupply. A plurality of code Wheels 65 aresecured to the shaft driven by the motor and function in a mannersimilar to that described in Fig. 2 to send out code signals indicativeof various conditions at the repeater station. The codesegments selectedby the code wheels a', b', c', d', e' and f cover predetermined non.-overlapping sections onV the periphery of the code wheels, each codewheel sending out a characteristic signal indicative of the condition ofa particular piece of equipment at the repeater station. Consideringcode wheel a.' as an example, this code rwheel will indicate whether ornot diode I8 is functioning in response to a minimum normal ofradiation. If normal radiation is occurring, the output from diode i8will operate relay in a manner previously described and close a. circuitover its contacts and over leads |36 Vand through thecode wheel tooperate relay ||2, this last relay, in turn, operating keyer 2l totransmit a characteristicV signal over lead |31 extending to the servicecircuit. Code wheelY b functions to indicate whether or not there isanoise level at the repeater station above adesired normal. For thispurpose there is provided av` relay |99 which is connected in theoutputy of.4

converter and rectifier 79, the latter in turn being connected to asuitable pick-up transmission line |26 coupled to the outputtransmission line |24. This noise level status can only be determinedwhen. the division center removes modulation from the carrier. Converterand rectifier 9 is a balanced detector circuit and therefore onlysupplies rectified current to relay m9 when there is-modulation on thecarrier. Obviously, if modulationis removed by the division center, theonly modulation which can operate relay |09 will be that-produced bynoise. The contacts of relay |09 are connected through leads |38 to thedisc wheelb to cause operation of relay ||2 when the segments on thedisc wheel b are engaging the spring contact associated therewith. Codewheel-c' indicates when relay is operated and consequently that publicservice power supply is connected to the system, while code wheel dindicates when relay is normal and consequently that the emergency orspare power contacts areemployed in order` that theV divisifln centermay be given a positive indication at all times of whether one or theother of the power supply equipment is being used, Code wheels e' and fserve to indicate which set of amplier eqmpment is being used. Forexample, if amplifiers 64 and 66 are being used, the switches it. and 2Qwill bedown (assuming the conditions prescribed above), relay |66 willbe operated and leads |39 from code wheel e will be closed through thecontacts of this relay. However, if the spare amplifier set comprising65 and 61 is being used underfthe conditions prescribed above, thenrelay I will be restored to normal and a path will be closed over leads|40 and the normally closed contacts of relay |66 to cause code wheel fto influence relay H2. It will be seen from an inspection of the drawingthat the shaft of the motor 25 is maintained at apositive potential andthat the code wheels directly mounted thereon are also maintained atthis potential, while a bus MI directly connected to the coil ||2 iscommon to one contact of the various, pairs of contacts associated withthe respective code wheels. As in the case of Fig. 2, the motor willcome to rest at the position where all contacts to the code wheels areopen.

When it is desired to shut down the repeating station, the divisioncenter will send out a tone. B which will be received over the servicecircuit and passed through selector 62 and am-f plied and rectified atto operate relay H33. The operation of this relay will break itsnormally closed contacts to open the return circuit of the magnet coilof relay H0, thus restoring relay HSB to normal. The restoration of thisrelay to normal removes power supply from the lsupply equipment isfunctioning, Both of these plates and filaments of the amplifiers whichpassed through the operated contacts of this relay. 'Ihe right-handcontacts of relay l0 will now be opened, thus opening the circuit ofleads |3| and |32 to prevent the operation of vrelay and insuring thatthe emergency power supply does not start up when the station is not inoperation. The return to normal of relay |||3 will also cause all therelays in the circuit to return to normal. It will thus be obvious thatthe shut down signal provided by tone B will set all relays so as toprevent the necessary functions of the apparatus at this station untilthe starting tone Ais again applied.

By the term timing used in the appended claims, I refer to the timing ofthe occurrence of similar portions of successive waves. If the frequencyis changed, the time between successive similar portions iscorrespondingly changed. Or, if the phase of a wave is shifted, the timeof occurrence of any wave portion is made earlier or later than in theabsence of such phase shift. Thus, the term timing modulation includesboth variation of frequency and variation oi phase. In contrast to this,in the case of amplitude modulation the timing of the occurrence ofsimilar portions of successive waves is unaffected by the modulation.

What is claimed is:

l. In a radio relaying system, a first station, a remote second station,and an intermediate station for relaying signals between said first andsecond stations, said intermediate station comprising a radio relayingstation having two sets of apparatus for alternatively performing thesame function, and circuit means at said station responsive to apredeterminedl signal arriving over one ofsaidother stations for-transmitting a characteristic signal indicating which one of said twosets is performing its intended function.

2. A relaying station for radio waves comprising a transmitting antenna,two amplifiers, and means responsive to a predetermined signal receivedby said station for automatically radiating over said antenna acharacteristic signal indicating which amplifier is operativelyassociated with said antenna, there being different characteristicsignals for said two amplifiers.

3. A relaying station for radio waves, electron discharge deviceequipment at said station, two 4 sets of power supply apparatus, andmeans responsive to a predetermined signal received by said station forautomatically radiating a characteristic signal indicating which set isoperatively associated with said electron discharge device equipment,there being different characteristic signals for said two sets of powersupply apparatus.

4. A relaying station for radio waves comprising a transmitting antenna,two amplifiers, two sets of power supply apparatus for said amplifiers,and means responsive to a predetermined signal received by said stationfor automatically radiating over said antenna characteristic signals insequence and in a predetermined order indicating which amplifier isoperatively associated with said antenna and which set of power supplyapparatus is operatively associated with the said amplifiers, therebeing different characteristic signals for said amplifiers and sets ofpower supply apparatus.

5. A radio relaying system comprising a central office, a remote stationin said system, said remote station having two sets of apparatus foralternatively performing the same function, and circuit means at saidremote station responsive to a predetermined signal from said centraloffice for transmitting to said central office a characteristic signalindicating which one of said two sets is performing its intendedfunction.

6:. A radio transmitting station having two sets of apparatus foralternatively performing the same function, a motor, a selectorresponsive to a predetermined signal for operating said motor, a shaftfor said motor, a pair of code wheels on said shaft, said wheels beingequipped with elements around the periphery thereof providing differentcodes for said sets of apparatus, contacts for each code wheel forengaging said elements, circuit means under control of the contacts onsaid code Wheels for transmitting characteristic signals correspondingto the codes on said wheels, and relay means controlled by at least oneof said sets for determining which one of said code wheels willoperatively affect said circuit means through its associated contacts,whereby the transmitted code signals indicate which one of said two setsof apparatus is performing its intended function.

7. A radio transmitting station having an amplifier and also a spareamplifier, power supply apparatus and also an emergency power supplyapparatus, a motor, a selector responsive to a predetermined signal foroperating said motor, a shaft for said motor, four code wheels on saidshaft, one for each of said ampliers and power supply apparatus, saidwheels having different codes provided by segments, the segments on thecode wheels associated with said amplifiers being located onsubstantially the same 180 portion but oppositely with respect to thesegments on the code wheels associated with said power supply apparatus,contacts for each code wheel, circuit means under control of thecontacts on said code wheels for transmitting characteristic signalsVcorresponding to the codes on said wheels, relay means controlled by atleast one of said amplifiers and additional relay means controlled by atleast one set of said power supply apparatus for respectivelydetermining which code wheel associated with said amplifiers and whichcode wheel associated with said power supply apparatus will effectivelyVoperate said circuit means to cause the same to send out the desiredcharacteristic signals upon rotation of said shaft.

8. A radio relaying system including a transmitting station radiatingamplitude modulated Waves, a repeating station for receiving saidradiated amplitude modulated waves, there being means at said repeaterstation for changing said amplitude modulated waves to frequencymodulated waves and for radiating said frequency modulated waves, and areceiving station for receiving the frequency modulated wavestransmitted by said repeating station.

9. A radio relay system for use at ultra short wavelengths comprising atransmitting station radiating amplitude modulated waves, a repeatingstation receiving said amplitude modulated waves and converting` them tofrequency modulated Waves having a different wavelength and forradiating said last waves, a second repeater station for receiving thewaves sent out by said first repeater station, means at said secondrepeater station for converting the received frequency modulated wavesto frequency modulated waves of a still different Wavelength and fortransmitting Waves of said still different wavelength, and a receivingstation for receiving the waves transmitted by said second repeaterstation.

10. A radio relaying station comprising an electron discharge deviceamplifier, power supply equipment, means responsive to a predeterminedsignal for connecting said power supply equipment to certain electrodesof said amplifier for conditioning the same to operate, means responsiveto 'another predetermined signal to disconnect said power supplyequipment from said amplifier, and` means responsive to a third anddifferent predetermined signal tor cause said station to transmit asignal indicative of the status of said amplifier.

11. A radio relay station comprising an electron discharge deviceamplifier, public service power supply terminals and spare power supplyterminals for said station, means at said `station responsive to apredetermined signal for connecting said amplifier to one of said powersupply terminals, means at said station responsive to anotherpredetermined signal to disconnect said last power supply terminals fromsaid amplifier, and means responsive to a third and differentpredetermined signal to cause said station to transmit a signalindicating which of said power supply terminals is connected to saidamplifier.

12. A radio relay station comprising a receiving element, a transmittingelement, amplifier apparatus adapted to be connected between saidelements, and means responsive to a predetermined signal for causingsaid station to transmit a characteristic signal indicating whether thenoise at said station is above normal, said means including radiofrequency pick-up apparatus coupled to saidtransmitting element and aconverter'and rectifier coupled to said pick-up apparatus.

13; A radiorelay station comprising a receiving element, a transmittingelement, amplier apparatus adapted to be connected between saidelements, and means responsive to a predetermined signal for causingsaid station to transmit a characteristic signal indicating Whether thenoise at said station is above normal, said means including thefollowing elements: a radio frequency pick-up apparatus coupled to saidtransmitting element, a converter and rectifier coupled to said pick-upapparatus, a motor, a selective circuit passing only said predeterminedsignal for operating said motor, a code wheel driven by said motor, acircuit operatively responsive to modulating energy in said converterand rectier and linking said converter and rectier to said code wheel,and keying means responsive to the rotation of said code wheel.

14. A radio relaying station comprising a receiving antenna, atransmitting antenna, a pair of ampliers adapted to be alternativelyconnected to said antennae, relays for controlling the operativeassociation of said amplifiers with said antennae, said relays havingholding coils, and means responsive to the reduction of radiation fromsaid station below a predetermined minimum for switching saidamplifiers, said means including a radio frequency pick-up member, arectier coupled to said pick-up member, and connections from the outputcf said rectifier to the holding coils of said relays, whereby reductionof current in the output of said rectifier below said predeterminedminimum reduces current in said holding coils and releases said relays.

15. A relaying station for radio waves comprising a transmittingcircuit, two amplifiers, and means responsive to a predetermined signalreceived by said station for automatically sending over said circuit acharacteristic signal indicating which amplifier is operativelyassociated with said circuit, there being diiierent characteristicsignals for said two ampliers.

16. A relaying station for radio waves, electron discharge deviceequipment at said station, two sets of power supply apparatus, and meansresponsive to a predetermined signal received by said station forautomatically transmitting a characteristic signal indicating which setis operatively associated with said electron discharge device equipment,there being different characteristic signals for said two sets of powersupply apparatus.

17. A radio relaying system including a transmitting station radiatingamplitude modulated waves, a repeating station for receiving saidradiated amplitude modulated waves, there being means at said repeaterstation for changing said amplitude modulated waves to waves modulatedas to timing and for radiating said last waves, and a receiving stationfor receiving the Waves transmitted by said repeating station.

l0 18. A radio relaying system including a transmitting stationradiating amplitude modulated waves, a repeating station for receivingsaid radiated amplitude modulated waves, there being means at saidrepeater station for changing said amplitude modulated waves to shorterwaves modulated as to timing and for radiating said last Waves, and areceiving station for receiving the waves transmitted by said repeatingstation.

Y 19. A radio relaying system including a transmitting station radiatingamplitude modulated waves, a repeating station for receiving saidradiated amplitude modulated waves, there being means at said repeaterstation for changing said amplitude modulated waves to frequencymodulated waves of shorter Wavelength than the received amplitudemodulated waves and for radiating said frequency modulated Waves, and areceiving station for receiving the frequency modulated Wavestransmitted by said repeating station.

20. A radio relay system for use at ultra short wavelengths comprising atransmitting station radiating amplitude modulated waves Whose length isof the order of six meters, a repeating station receiving said amplitudemodulated waves and converting them to frequency modulated waves havinga shorter wavelength below one f meter and for radiating said lastwaves, a second repeater station for receiving the waves sent out bysaid first repeater station, means at said second repeater station forconverting the received frequency modulated Waves to frequency modulatedWaves of a still different wavelength but also below one meter and fortransmitting waves of said still dilerent wavelength, and a receivingstation for receiving the waves transmitted by said second repeaterstation.

FRED H. KROGER.

